1. Field of the Invention
This invention relates to a data carrier, in particular a paper of value, identity card or the like, which is provided with an optically variable security element having optically variable pigments without, or with only weak, body color of their own.
2. Description of the Prior Art
There have been manifold efforts lately to mark data carriers and protect them from falsification or forgery. In particular the improved quality of photocopiers has caused optically variable elements to be increasingly applied to security documents whose optically variable effect is not reproducible by copying machines.
For example it is known from EP 0 317 514 A1 to apply to a document a layer with iridescent substances which conveys a different color effect at different viewing angles. It is in particular proposed that the iridescent substance be applied flat to a subjacent, black, all-over layer. In a further working step the thus produced iridescent surface can be overlaid with information by overprinting this surface.
EP 0 435 029 A3 furthermore discloses the use of liquid-crystal polymers as optically variable elements whereby a color tilting effect arises upon a change of viewing or lighting angle. This effect is based substantially on the helical structure of the liquid-crystal phase, which can be fixed by crosslinking in polymers and furthermore adjusted via external conditions, such as mechanical pretreatment. This also makes it possible to selectively adjust the color tone of the color change.